沙颍河表层沉积物中氮与重金属的分布特征及污染评价

为揭示沙颍河沉积物中氮及重金属的分布和污染特征,于2015年6—9月采集了沙颍河干支流主要站点的表层沉积物及上覆水样品,分析了其中氮的赋存形态和重金属的分布,探讨了水体-沉积物氮的转化机制及重金属的来源。结果表明:沙颍河表层沉积物中NO-3-N、NH+4-N、ON(有机氮)和TN的质量比分别为21.47~53.60 mg/kg、1.702 3~3.066 1 mg/kg、1 050~2 390 mg/kg和1 071~2 488 mg/kg,ON占TN的97.17%以上;表层沉积物中Cd、Cu、Zn和As质量比分别为1.583~3.533 mg/kg、21.98~64.60 mg/kg、148.5~165.5 mg/kg和1.527~2.416 mg/kg。Pearson相关性分析表明:表层沉积物中氮主要存在于有机物中,表层沉积物释放NH+4-N已经成为影响沙颍河水体NH+4-N浓度的一个重要因素;沙颍河大部分站点的表层沉积物有机指数和ON分别处于Ⅱ、Ⅳ级,有机碳污染较轻,ON污染严重;潜在生态评价中重金属Cd已经达到了很强-极强的污染程度,其余重金属则处于轻微污染水平;重金属潜在生态风险指数IR显示沙颍河表层沉积物重金属潜在风险已经到了很强-极强的水平,其中Cd对IR的贡献达97.22%。

Distribution Pattern of Heavy Metals in the Surface Sediments of the Jiaozhou Bay

Grain size analysis and chemical analysis of heavy metals are made for 312 surface samples of the Jiaozhou Bay. Nineteen samples of the waste water taken from the sewage discharge outlets along the eastern coast of the bay are also analyzed for heavy metals. Results show that heavy metals are richer in the east and poorer in the west of the bay. Sedimentary dynamic studies reveal that the distribution of heavy metals in the surface sediments of the Jiaozhou Bay is under the control of hydrodynamics.

Sedimentary response to volcanic activity in the Okinawa Trough since the last deglaciation

To investigate the relationship between volcanic activity and sediment record on regional and temporal scales,158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT),and two cores recovered in the northern and southern OT,respectively.Mineralogy,grain-size,and geochemical analyses of those samples show that:1) volcanic glass,volcanic-type pyroxene,hypersthenes,and magnetite increase in sediment influenced by volcanic activity;2) sediment grain sizes (and also silt content) increase in ash layers;and 3) the contents of Na2O and Zr are higher,while terrigenous elements,e.g.,TFe2O3 and K2O,and biogenous compositions,e.g.,CaO and Sr,are relatively lower in ash layers than those of non-ash layers.The distribution of volcanic ash has three distinguishing characteristics:1) volcanic ash is more abundant in the northern and central OT than the southern OT;2) volcanic ash increases from continental shelf to the trough;3) the sediment during the last 12 000 a suggests stronger volcanic events than during 15 000-12 000 a.The eruptive locations,frequency,and volume of calderas are among the most important factors controlling the distributions of volcanic ash.In addition,the main Kuroshio warm current that extends northward probably impeded the diffusion of volcanic ash to the west and south in the OT.However,a southward current probably carried some volcanic ash toward southern OT.

Laboratory Application of Laser Grain-Size Analyzer in Determining Suspended Sediment Concentration

Suspended sediment concentration(SSC) is an important parameter in marine sedimentology. With the development of technology, many acoustic and optical devices, such as the Laser In-Situ Scattering and Transmissometry, have been designed to measure in situ SSC and grain size distribution. But due to fund or other restrictions, many experiments were only conducted in laboratory, using an indoor laser grain-size analyzer and gravimetric method to measure grain size distribution and concentration, respectively. In this study the laboratory experiment is simplified by omitting the tiring step of gravimetric method. The connections between SSC and other parameters(obscuration, D50 and sorting index) were investigated based on 124 surface sediment samples collected from different offshore areas. A new method is developed for determining SSC in laboratory using a laser grain-size analyzer.

End member inversion of surface sediment grain size in the South Yellow Sea and its implications for dynamic sedimentary environments

Four end members were inverted from surface sediment grain size data from the South Yellow Sea by using the end member(EM) model. The sediment provenance and hydrodynamic meanings of each EM were discussed based on the frequency and spatial distributions of the EMs. EM1 and EM2 reflect the dynamic transport and sorting processes of the terrigenous sediment, and EM3 and EM4 reflect the modification of relic sand. The ocean front mainly affected transport of relatively coarse terrigenous sediment in the South Yellow Sea, and the fine terrigenous sediments were generally unaffected by the ocean front. Fine sediment could pass through the ocean front and deposit in the central South Yellow Sea under weak tidal condition to form most part of the Central Yellow Sea Mud(CYSM). The CYSM extended toward northwest and southwest. The sediment in the north part of the CYSM mainly consisted of sediment from the Yellow River(Huanghe) in the northwest, and the sediment in the southwest part of CYSM mainly consisted of Subei coastal sediments from both the Yangtze River(Changjiang) and the Yellow River. Compared to the traditional method of sediment grain size analysis, the EM model can determine the EMs and provide better explanations of the sediment provenance and dynamic regional sedimentary environment in the study area.

Modern pollen assemblages from surface lake sediments in northwestern China and their importance as indicators of vegetation and climate

The modern pollen assemblages of surface lake sediments and topsoils in northwestern China were studied to understand the relationship of modem pollen data with contemporary vegetation and climate, and the differences between the pollen assem- blages of surface lake sediments and topsoils. The results show that Chenopodiaceae and Artemisia are dominant elements in the pollen assemblages of northwestern China. Additionally, Ephedra, Cyperaceae, Asteraceae, Poaceae, Picea, Pinus, and Betula are also important pollen taxa. Both pollen assemblages and principal component analysis indicate that pollen data from surface lake sediments and topsoils can be used to differentiate the main vegetation types of this region （desert, steppe, mead- ow and forest）. However, differences exist between modern pollen assemblages of the two types of sediments due to the dif- ferent relevant source areas of pollen and degrees of pollen preservation. For example, the larger relevant source area of sur- face lake sediment results in a higher abundance of Betula in pollen assemblage from surface lake sediment, whereas the ten- dency to disintegrate thin-walled pollen types in topsoil leads to a higher proportion of resistant pollen, such as Asteraceae. Linear regression analysis indicates that the Artemisia/Chenopodiaceae （A/C） ratio in pollen assemblages of surface lake sedi- ments can be used to indicate humidity changes in the study area. However, the A/C ratio in topsoils should be used carefully. Our results suggest that pollen data from surface lake sediments would be better references for interpreting the fossil pollen assemblages of lake cores or lacustrine profiles.

Distinct distribution revealing multiple bacterial sources for 1-Omonoalkyl glycerol ethers in terrestrial and lake environments

The 1-O-monoalkyl glycerol ethers （MAGEs） were initially viewed as the biomarkers for sulfate-reducing bacteria （SRB） me- diating anaerobic oxidation of methane in the marine environments. However, limited information is known about their distri- bution in terrestrial and other aquatic settings including soils, fresh water lakes, and cave sediments, which may obscure our understanding of their biological sources. Here we found that MAGEs were ubiquitous but differed obviously in distributional pattern among those environments. The surface soils are dominated generally by iC15：0-MAGE, followed by nCI6：o-MAGE whereas the lake sediments show the opposite, resulting in significantly higher iC15：0/nC16：0 ratios in soils than in lake sedi- ments. The cave deposits are characterized by considerably higher proportions of branched MAGEs than the former two envi- ronments. The logarithm of iC15：0/aC15：0 ratio shows a significant negative correlation with soil pH, likely reflecting an adapta- tion of microbial cell membrane to change in the ambient proton concentration. The MAGE profiles in cultured bacteria cannot fully explain the MAGE distribution in all the samples analyzed. Therefore, MAGEs in soil, lake sediments, and cave deposits likely have additional biological source（s） other than SRB and cultured MAGE-producing bacteria. The difference in MAGE pattern among environments is likely to be attributed to change in microbial communities.